It is widely known that various organometallic compounds and asphaltenes are present in petroleum crude oils and other heavy petroleum hydrocarbon streams, such as petroleum hydrocarbon residua, hydrocarbon streams derived from tar sands, and hydrocarbon streams derived from coals. The most common metals found in such hydrocarbon streams are nickel, vanadium, and iron. Such metals are very harmful to various petroleum refining operations, such as hydrocracking, hydrodesulfurization, and catalytic cracking. The metals and asphaltenes cause interstitial plugging of the catalyst bed and reduced catalyst life. The various metal deposits on a catalyst tend to poison or deactivate the catalyst. Moreover, the asphaltenes tend to reduce the susceptibility of the hydrocarbons to desulfurization. If a catalyst, such as a desulfurization catalyst or a fluidized cracking catalyst, is exposed to a hydrocarbon fraction that contains metals and asphaltenes, the catalyst will become deactivated rapidly and will be subject to premature removal from the particular reactor and replacement by new catalyst.
Various materials have been employed in the treatment of petroleum hydrocarbon streams for the removal or substantial reduction of the metals and asphaltenes contained therein. For example, such treatment may have been conducted with bauxite (U.S. Pat. Nos. 2,687,985 and 2,769,758); a material consisting essentially of titania and alumina (U.S. Pat. No. 2,730,487); a material consisting essentially of iron oxide and alumina (U.S. Pat. No. 2,764,525); fresh or spent bauxite, activated carbon, artificial and synthetic clays, and silica-alumina materials (U.S. Pat. No. 2,771,401); and a porous alumina having extensive macroporosity, the latter being in an ebullated bed (U.S. Pat. No. 3,901,792).
Moreover, silica can also be used to treat a heavy hydrocarbon stream containing metals and/or asphaltenes. For example, a metals-free hydrocarbon distillate can be produced by a combination process comprising at least two fractionation steps coupled with a hydrotreating step employing a catalyst comprising a porous refractory support, such as silica, alumina, zirconia, titania, or combinations of these with each other or with small amounts of acid-acting substances, such as halogen, phosphates, etc., and one or more hydrogenation metals from Groups VI, VII, and VIII of the Periodic Table of Elements (U.S. Pat. No. 2,944,013).
It has been disclosed that the catalytic hydrodesulfurization of heavy oils with high contents of ash-forming contaminants, such as vanadium complexes, is facilitated by a prior cracking of the oil maintained largely in the liquid phase in the presence of comminuted solids with extended surfaces and preferably absorptive surfaces like clay, iron ore, alumina, and silica gel, with or without hydrogen (U.S. Pat. No. 2,987,467).
In an integrated process, a residual hydrocarbon oil containing metal contaminants (nickel and vanadium) is first hydrogenated either with a hydrogen donor diluent or over a catalyst having one or more hydrogenation promoting metals supported on a solid carrier exemplified by alumina or silica and then vacuum distilled to separate a heavy gas oil fraction containing reduced quantities of metals from an undistilled residue boiling primarily above about 1,100.degree. F. and containing asphaltic material. The heavy gas oil fraction is subsequently catalytically cracked (U.S. Pat. No. 3,162,596).
A heavy hydrocarbon stock may be upgraded in a two-zone hydrodesulfurization process (U.S. Pat. No. 3,180,820). Each zone employs a solid hydrogenation catalyst comprising one or more metals from Groups VB, VIB, and VIII of the Periodic Table of Elements. Either catalyst may be supported or unsupported. In a preferred embodiment, the first zone contains an unsupported catalyst-oil slurry and the second zone contains a supported catalyst in a fixed bed, slurry, or fluidized bed. A rather broad, general, vague and indefinite shot-gun-type disclosure provides that the support of a supported catalyst may be a porous refractory inorganic oxide carrier, including alumina, silica, zirconia, magnesia, titania, thoria, boria, strontia, hafnia, and complexes of two or more oxides such as silica-alumina, silica-zirconia, silica-magnesia, alumina-titania, and silica-magnesia-zirconia, among others. The patent provides that the supported catalyst appropriate for use in the invention will have a surface area of about 50 to 700 square meters per gram, a pore diameter of about 20 to 600 Angstrom units (A), and a pore volume of about 0.10 to 20 milliliters per gram. However, it does not indicate which values pertain to which particular support. Moreover, the working examples consider only supports comprising combinations of oxides, i.e., an equimolar alumina-silica carrier and an alumina-silica-boron-phosphate carrier.
Catalysts comprising metals of Group VI and Group VIII on a support selected from silica, oxides of metals in Groups IIA, IIIA, and IVB, and mixtures thereof are disclosed for the removal of metal-containing compounds in an initial hydrocracking operation to protect the catalyst in a subsequent hydrogenation stage (U.S. Pat. No. 3,472,759).
In an improved process for hydrotreating a petroleum hydrocarbon stream containing metals and asphaltenes, the feed is contacted first with a particulate solid having a plurality of pores, the size of which range from 1,000 A to 50,000 A, and containing at least one member selected from the group consisting of iron, cobalt, nickel, tungsten, chromium, molybdenum, and vanadium, prepared by mixing refractory particles of a specified particle size range with an alumina hydrogel, to eliminate asphaltic and metallic components from the feed, and then the pretreated hydrocarbons are hydrotreated in the presence of a catalyst of Group VI and/or Group VIII metal on a silica-alumina carrier. It was disclosed that the use of active carbon, aluminum hydroxide, aluminum oxide, synthetic silica, inter alia, as the catalyst in the first step demonstrated drawbacks and resulted in not fully satisfying the purpose of the preliminary treatment (U.S. Pat. No. 3,530,066).
There has now been found and developed a new process for treating a heavy petroleum hydrocarbon stream that contains metals and asphaltenes, which process comprises contacting in a reaction zone the heavy petroleum hydrocarbon stream under appropriate conditions with a particular catalyst to produce an effluent that contains appreciably less metals and less asphaltenes than the stream that was treated in such process. The product obtained from this process may be used conveniently as a feedstock to a hydrodesulfurization zone or as a feedstock to a catalytic cracking zone.